When pastors gaze out from their pulpits, they may want to imagine what would happen if they asked their flocks to respond to this statement: "As long as it's between consenting adults, any kind of sex is fine."

If this were a conservative or nondenominational Protestant church, the active, "practicing" members would be sharply divided, according to a new Barna Group survey. Nearly half -- 46 percent -- would affirm this live-and-let-live approach to sex outside of marriage, while 40 percent would disagree "strongly" and 12 percent "somewhat."

There are the active members, not the people who occasionally visit the pews.

"What is surprising is the way that even practicing Christians are beginning to conform to the beliefs and behaviors that are now considered normal in our culture," said Roxanne Stone, editor-in-chief at Barna. "The big story here is that people no longer agree when it comes to the purpose and meaning of sex -- including in our churches. Many no longer connect sex and marriage the way they used to."

When looking at broader trends, this study found the usual evidence that older Americans -- the "Elders" and "Boomers" -- have much more traditional views of sex and marriage than members of the younger "Gen-X" and "Millennial" generations. Rising numbers of young Americans view sex through the lens of self-expression and personal growth, with few ties that bind them to institutions and traditions.

"What people are saying is that sex is about two people loving each other and experiencing intimacy, but you don't really need to have the word 'marriage' involved in this discussion," said Stone, in a telephone interview.

"It's surprising how quickly some of these changes have become part of what is now considered normal. … Normally, these kinds of radical changes in a culture evolve over time. But, sociologically speaking, Woodstock wasn't that long ago."